Ecological impacts of the microsporidian parasite Pleistophora mulleri on its freshwater amphipod host Gammarus duebeni celticus

Parasitology ◽  
2005 ◽  
Vol 131 (3) ◽  
pp. 331-336 ◽  
Author(s):  
N. J. FIELDING ◽  
C. MacNEIL ◽  
N. ROBINSON ◽  
J. T. A. DICK ◽  
R. W. ELWOOD ◽  
...  
Keyword(s):  
Interspecific Interactions ◽  
Parasite Burden ◽  
Parasite Prevalence ◽  
Abdominal Muscle ◽  
Host Population ◽  
Ecological Impacts ◽  
Activity Level ◽  
Microsporidian Parasite ◽  
Individual Host ◽  
Invasive Amphipod

The microsporidian parasite, Pleistophora mulleri, infects the abdominal muscle of the freshwater amphipod Gammarus duebeni celticus. We recently showed that P. mulleri infection was associated with G. d. celticus hosts being more vulnerable to predation by the invasive amphipod Gammarus pulex. Parasitized G. d. celticus also had a reduced ability to prey upon other co-occurring amphipods. We suggested the parasite may have pervasive influences on host ecology and behaviour. Here, we examine the association between P. mulleri parasitism and parameters influencing individual host fitness, behaviour and interspecific interactions. We also investigate the relationship between parasite prevalence and host population structure in the field. In our G. d. celticus study population, P. mulleri prevalence was strongly seasonal, ranging from 8·5% in summer to 44·9% in winter. The relative abundance of hosts with the heaviest parasite burden increased during summer, which coincided with high host mortality, suggesting that parasitism may regulate host abundance to some degree. Females were more likely to be parasitized than males and parasitized males were paired with smaller females than unparasitized males. Parasitism was associated with reduction in the host's activity level and reduced both its predation on the isopod Asellus aquaticus and aggression towards precopula pairs of the invasive G. pulex. We discuss the pervasive influence of this parasite on the ecology of its host.

scholarly journals Influence of acculturation among Tunisian migrants in France and their past/present exposure to the home country on diet and physical activity

2009 ◽  
Vol 12 (6) ◽  
pp. 832-841 ◽  
Author(s):  
Caroline Méjean ◽  
Pierre Traissac ◽  
Sabrina Eymard-Duvernay ◽  
Francis Delpeuch ◽  
Bernard Maire
Keyword(s):  
Physical Activity ◽  
Physical Activity Level ◽  
Social Ties ◽  
Home Country ◽  
Host Population ◽  
Activity Level ◽  
Lower Percentage ◽  
Percentage Contribution ◽  
Salt Consumption ◽  
Current Exposure

AbstractObjectiveTo study how dietary patterns and physical activity vary with acculturation and with past and current exposure to socio-cultural norms of the home country among Tunisian migrants.DesignA retrospective cohort study was conducted using quota sampling (n 150) based on age and residence. Dietary intake was assessed using a validated FFQ. Physical activity level and dietary aspects were compared according to length of residence (acculturation), age at migration (past exposure) and social ties with the home country (current exposure).Subjects and settingTunisian migrant men residing in the South of France.ResultsMigrants who had lived in France for more than 9 years had a higher percentage contribution of meat to energy intake (P = 0·04), a higher Na intake (P = 0·04), a lower percentage contribution of sugar and sweets (P = 0·04) and a lower percentage of carbohydrates (P = 0·03) than short-term migrants. Men who migrated before 21 years of age had a higher Na intake than ‘late’ migrants (P = 0·02). Men who had distant social ties with Tunisia had a lower physical activity level (P = 0·01) whereas men who had close ties had a higher percentage of fat (P = 0·01) and a higher ratio of MUFA to SFA (P = 0·02).ConclusionsAcculturation led to a convergence of some characteristics to those of the host population, while some results (meat and salt consumption) were at variance with other acculturation studies. Past and current exposure to the home country helped maintain some positive aspects of the diet. Nevertheless, present dietary changes in Tunisia could soon lessen these features.

Patterns of variation in parasite component communities and infracommunities of a littoral fish species from the northern coast of Chile

2012 ◽  
Vol 88 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Vania Henríquez ◽  
M. Teresa González
Keyword(s):  
Fish Population ◽  
Host Population ◽  
Northern Coast ◽  
Component Community ◽  
Geographic Scale ◽  
Parasite Communities ◽  
Individual Host ◽  
Hierarchical Levels ◽  
Geographical Scale ◽  
Parasite Assemblages

AbstractThe structure and similarity of the parasite communities of fish can be evaluated at the component community (CC) and infracommunity (IC) levels. Both hierarchical levels have been used to assess parasite variations in fish at large (biogeographic) scales. However, studies evaluating the consistency between these two hierarchical levels at smaller geographical scales are scarce. In this study, the parasite assemblages of 124 Paralabrax humeralis collected by local fishermen by spear fishing at four sites (El Fierro, EF; P. Angamos, PA; Santa María, ISM; San Jorge, BSJ) in northern Chile were compared to assess the variability (or similarity) of their CCs and ICs at a limited geographical scale using multivariate analysis. At the IC level, discriminant analyses showed that P. humeralis parasite communities varied significantly among sites; 70% of ectoparasite ICs were correctly assigned to each site, but only 55% of helminth parasite ICs were correctly classified. At the CC level, the composition of parasite communities as assessed by correspondence analyses varied significantly between sites. Tagia sp., Neobenedenia sp. and Philometra sp. were associated with BSJ, ISM and PA, respectively; Corynosoma sp. and most digeneans were associated with both ISM and EF. Analysis of similarities (ANOSIM) showed significant variations in the degree of similarity between P. humeralis CCs from different sites, but not between ICs. Variations between CCs from different sites reflect fish population processes (e.g., population age, reproductive segregation) and the particular conditions of their respective habitats, whereas ICs reflect individual host movements. This study demonstrated that, when examined at a limited geographical scale, IC is better than CC at capturing the local pool of parasite assemblages when host populations are spatially segregated. Therefore, in this study, it is demonstrated that at a small geographic scale, CC variations are not reflected by IC, when host population is spatially segregated.

The regulation of host population growth by parasitic species

Parasitology ◽  
1978 ◽  
Vol 76 (2) ◽  
pp. 119-157 ◽  
Author(s):  
R. M. Anderson
Keyword(s):  
Population Growth ◽  
Reproductive Potential ◽  
Parasite Burden ◽  
Host Population ◽  
Parasitic Species ◽  
Regulatory Influence ◽  
Host Mortality ◽  
Parasite Reproduction ◽  
Over Dispersion ◽  
Host Parasite

SummaryThe nature of parasitism at the population level is defined in terms of the parasite's influence on the natural intrinsic growth rate of its host population. It is suggested that the influence on this rate is related to the average parasite burden/host and hence to the statistical distribution of parasites within the host population.Theoretical models of host–parasite associations are used to assess the regulatory influence of parasitic species on host population growth. Model predictions suggest that three specific groups of population processes are of particular importance: over-dispersion of parasite numbers/host, density dependence in parasite mortality or reproduction and parasite-induced host mortality that increases faster than linearly with the parasite burden. Other population mechanisms are shown to have a destabilizing influence, namely: parasite-induced reduction in host reproductive potential, direct parasite reproduction within the host and time delays in the development of transmission stages of the parasite.These regulatory and destabilizing processes are shown to be commonly observed features of natural host-parasite associations. It is argued that interactions in the real world are characterized by a degree of tension between these regulatory and destabilizing forces and that population rate parameter values in parasite life-cycles are very far from being a haphazard selection of all numerically possible values. It is suggested that evolutionary pressures in observed associations will tend to counteract a strong destabilizing force by an equally strong regulatory influence. Empirical evidence is shown to support this suggestion in, for example, associations between larval digeneans and molluscan hosts (parasite-induced reduction in host reproductive potential counteracted by tight density-dependent constraints on parasite population growth), and interactions between protozoan parasites and mammalian hosts (direct parasite reproduction counteracted by a well-developed immunological response by the host).The type of laboratory and field data required to improve our understanding of the dynamical properties of host–parasite population associations is discussed and it is suggested that quantitative measurement of rates of parasite-induced host mortality, degrees of over-dispersion, transmission rates and reproductive and mortality rates of both host and parasite would provide an important first step. The value of laboratory work in this area is demonstrated by reference to studies which highlight the regulatory influence of parasitic species on host population growth.

scholarly journals The epidemiological consequences of optimisation of the individual host immune response

Parasitology ◽  
2002 ◽  
Vol 125 (7) ◽  
pp. S61-S70 ◽  
Author(s):  
G. F. MEDLEY
Keyword(s):  
Parasite Burden ◽  
Resource Acquisition ◽  
Reproductive Value ◽  
Continuous Exposure ◽  
Use Of Resources ◽  
Trade Offs ◽  
Individual Host ◽  
Survival And Reproduction ◽  
The Individual ◽  
Simultaneous Variation

We present a simple unscaled, quantitative framework that addresses the optimum use of resources throughout a host's lifetime based on continuous exposure to parasites (rather than evolutionary, genetically explicit trade-offs). The principal assumptions are that a host's investment of resources in growth increases its survival and reproduction, and that increasing parasite burden reduces survival. The host reproductive value is maximised for a given combination of rates of parasite exposure, host resource acquisition and pathogenicity, which results in an optimum parasite burden (for the host). Generally, results indicate that the optimum resource allocation is to tolerate some parasite infection. The lower the resource acquisition, the lower the proportion of resources that should be devoted to immunity, i.e. the higher the optimum parasite burden. Increases in pathogenicity result in reduced optimum parasite burdens, whereas increases in exposure result in increasing optimum parasite burdens. Simultaneous variation in resource acquisition, pathogenicity and exposure within a community of hosts results in overdispersed parasite burdens, with the degree of heterogeneity decreasing as mean burden increases. The relationships between host condition and parasite burden are complicated, and could potentially confound data analysis. Finally, the value of this approach for explaining epidemiological patterns, immunological processes and the possibilities for further work are discussed.

Transmission dynamics of Echinococcus multilocularis; its reproduction number, persistence in an area of low rodent prevalence, and effectiveness of control

Parasitology ◽  
2005 ◽  
Vol 131 (1) ◽  
pp. 133-140 ◽  
Author(s):  
K. TAKUMI ◽  
J. VAN DER GIESSEN
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Central Europe ◽  
Definitive Host ◽  
Echinococcus Multilocularis ◽  
Reproduction Number ◽  
Parasite Burden ◽  
Host Population ◽  
Total Biomass ◽  
Control Campaign

On the basis of high prevalences of Echinococcus multilocularis in the growing fox populations in Central Europe, its total biomass may have increased significantly in the past 20 years. E. multilocularis is now also found in areas outside the known endemic area in Central Europe. Therefore, E. multilocularis, the causative agent of a serious parasitic zoonosis, might be of major concern for public health and a challenge to control. Some experimental field trials to control E. multilocularis using an anti-worm drug reduced parasite burden in a contaminated region during the control campaign, but failed to eradicate the parasite completely. It was our aim to develop a mathematical model describing the biomass of egg, larval, and adult worm stages of the E. multilocularis life-cycle, and simulate a hypothetical control campaign. Additionally, we derived the reproduction number of this parasite and explored conditions for the persistence of the parasite's life-cycle. Our model shows that while control campaigns rapidly reduce the worm burden in the definitive host, and consequently eggs in the environment, the pool of larvae in the intermediate host remains large. The parasite's life-cycle persists in a region where prevalence in the intermediate host is low (∼1%). Therefore, we conclude that the parasite is likely to re-emerge if control is discontinued on the basis of reduced worm population. Continued treatment of the definitive host is required to eradicate the larval stage of the parasite from the intermediate host population.

Quantifying the impact of disease on threatened species

1994 ◽  
Vol 1 (2) ◽  
pp. 107 ◽  
Author(s):  
Hamish McCallum
Keyword(s):  
Threatened Species ◽  
Parasitic Infection ◽  
Parasite Burden ◽  
Experimental Manipulation ◽  
Major Effect ◽  
Host Population ◽  
Bacterial Disease ◽  
Substantial Impact ◽  
High Prevalence ◽  
The Impact

Determining whether a disease or parasite is having a substantial impact on a population of a threatened species is not straightforward. Highly pathogenic parasites are not those which have the greatest influence on hosts, and diseases present at high prevalence are not likely to have a major effect on the host population. I develop simple mathematical models which show that a microparasitic disease such as a viral or bacterial disease will have the greatest impact on its host if it prevents host reproduction, but does not affect host mortality. If infected hosts can still reproduce, intermediate levels of pathogenicity have the greatest impact on hosts. Macroparasites such as helminths likewise have maximum impact on hosts at intermediate pathogenicity. The impact of a helminth on its host population is, however, determined by a complex interplay between pathogenicity per parasite and the nature of the host response to infection. For example, in the absence of density-dependent constraints on parasites within individual hosts, the smaller the impact per parasite on the host, the greater the impact of the parasitic infection on the overall population. Several recommendations can be made to wildlife managers who detect a disease or parasite and wish to determine its impact on a population of a threatened species. There is no entirely satisfactory alternative to experimental manipulation. Treating part of a population and comparing suvivorship or fecundity with controls is the only way to confirm the impact of a disease on a free-ranging population. Such an approach is impractical with every potential pathogen in a population. Some idea as to which pathogens may be of significance to the population can be gained from comparison of disease prevalence or parasite burden between dead and dying hosts and the overall population. Overall high prevalence or high pathogenicity are not good indicators on their own.

scholarly journals Sex-biased differences in the effects of host individual, host population and environmental traits driving tick parasitism in red deer

2013 ◽  
Vol 3 ◽  
Author(s):  
Francisco Ruiz-Fons ◽  
Pelayo Acevedo ◽  
Raquel Sobrino ◽  
Joaquín Vicente ◽  
Yolanda Fierro ◽  
...  
Keyword(s):  
Red Deer ◽  
Host Population ◽  
Host Individual ◽  
Individual Host

scholarly journals An avian dominance hierarchy at a supplemental water source in the Patagonian steppe

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244299
Author(s):  
Sophie Rabinowicz ◽  
Natalia García ◽  
Tristan Herwood ◽  
Amanda Lazar ◽  
Benjamin Hein ◽  
...  
Keyword(s):  
Dominance Hierarchy ◽  
Interspecific Interactions ◽  
Water Source ◽  
Ecological Impacts ◽  
Avian Species ◽  
Food Supplementation ◽  
Scarce Resources ◽  
Interacting Species ◽  
Interspecific Dominance ◽  
The Difference

Birds often compete and engage in interspecific agonistic interactions for access to resources such as food and breeding territories. Based on the observed outcomes from such interactions (i.e., patterns of displacements) dominance hierarchies can be established. Knowing which species can outcompete others for essential resources allows researchers to make predictions about the broader ecological impacts of interspecific interactions. We constructed an interspecific dominance hierarchy of twelve avian species which visited an artificial water source in an arid region of coastal Patagonia, Argentina. Displacements were categorized into four types, based on the behaviors involved in the interaction, and we tested if they could predict the difference in dominance between the interacting species (the difference between calculated dominance coefficients for the two focal species). Indirect displacements, involving only the arrival of the dominant species to the water source without direct aggression toward the subordinate bird, occurred more frequently between species with a large difference in dominance. The most dominant bird observed was the kelp gull (Larus dominicanus), which, due to an increasing population and expanding range, in part due to food supplementation from fisheries waste, is likely to outcompete terrestrial and marine avian species for other scarce resources.

scholarly journals A review of mathematical models of influenza A infections within a host or cell culture: lessons learned and challenges ahead

2021 ◽  
Author(s):  
Catherine A. A. Beauchemin ◽  
Andreas Handel
Keyword(s):  
Public Health ◽  
Cell Culture ◽  
Mathematical Models ◽  
Influenza A ◽  
Influenza Infection ◽  
Population Level ◽  
Host Population ◽  
Lessons Learned ◽  
Infection Dynamics ◽  
Individual Host

Most mathematical models used to study the dynamics of influenza A have thus far focused on the between-host population level, with the aim to inform public health decisions regarding issues such as drug and social distancing intervention strategies, antiviral stockpiling or vaccine distribution. Here, we investigate mathematical modeling of influenza infection spread at a different scale; namely that occurring within an individual host or a cell culture. We review the models that have been developed in the last decades and discuss their contributions to our understanding of the dynamics of influenza infections. We review kinetic parameters (e.g., viral clearance rate, lifespan of infected cells) and values obtained through fitting mathematical models, and contrast them with values obtained directly from experiments. We explore the symbiotic role of mathematical models and experimental assays in improving our quantitative understanding of influenza infection dynamics. We also discuss the challenges in developing better, more comprehensive models for the course of influenza infections within a host or cell culture. Finally, we explain the contributions of such modeling efforts to important public health issues, and suggest future modeling studies that can help to address additional questions relevant to public health.

Sign in / Sign up

Export Citation Format

Share Document